Quality extract of Ginkgo biloba,a 240 mg per day, if taken alone or 120 mg per day if taken with 200 mg per day of Panax ginseng Huperzine A, 200 mg, 2 times per day aUse of ginkgo should be stopped prior to surgery to prevent bleeding. Patients should tell physicians about taking ginkgo for this reason.
If additional interventions to maintain cognition become warranted, one of the first considerations, and by far the most popular one, is ginkgo (Ginkgo biloba). It is by way of various mechanisms of action, perhaps most notably inhibition of lipid peroxidation, that ginkgo may help to preserve, and to some extent restore, healthy cognition. Extracts of ginkgo have been shown to act as free-radical scavengers, preventing induced lipid peroxidation of neural tissue under several experimental conditions.11,12 A review of the literature also suggests that additional actions, such as a relaxing effect on vascular walls, inhibition of platelet-activating factor, enhancement of microcirculation, and stimulation of neurotransmitters,13 could all contribute to ginkgo being a multifaceted therapeutic agent for patients with dementia (see the box below entitled "How Ginkgo biloba Supports Cognition'').
In the context of already existing dementia, botanical medicines may prove to be some of the most effective treatment options available.
It would be remiss, however, not to acknowledge that, while many trials show benefit with the use of ginkgo,14,15 there are notable exceptions. A 24-week trial failed to show any benefit of ginkgo for more than 200 elderly subjects with dementia.16 Such results stand in sharp contrast to those of other trials, such as a year-long study of more than 300 subjects with dementia who received only 120 mg of an extract of this herb and who manifested stabilized or even improved cognitive performance for six months to a year during the study.17 In such situations, when data from peer-reviewed sources seem to disagree, it is important to remember that many factors may combine to skew the data of one, or even several studies, in a particular direction. A recent review of the ginkgo literature points out that discrepancies between results of one study and another may be the result of factors such as the study population used, the outcome measures utilized, the duration of treatment, and the dosing regimen of the subjects.18 Additionally, many of the studies utilize a particularly potent form of ginkgo, EGb 761, which is a standardized extract of dried leaves containing 24% ginkgo-flavonol glycosides, 6% ter-pene lactones such as ginkgolides A, B, C, J and bilobalide. Thus, variations in study outcomes may be related to the potency and form of ginkgo used in the trials. Generally, the literature seems to support the benefit of ginkgo extract for subjects with dementia. Also, equally important is that, clinically, ginkgo has repeatedly demonstrated itself to be an effective and safe intervention.
How Ginkgo biloba Supports Cognition
Inhibition of free-radical damage to Relaxation of vascular walls lipid neural tissue Increase in local blood flow
Inhibition of platelet-activating factor Increase in neurotransmitter activity
In addition to senior subjects with dementia, however, there is also evidence that ginkgo extract may enhance memory for those who are younger. In a smaller study of 20 subjects, volunteers were given 120 mg, 240 mg, or 360 mg of Ginkgo biloba extract or a placebo. A series of computerized tests was then done to assess speed and accuracy of attention and speed and quality of memory. The most striking change was a dose-dependent improvement in the speed of attention that was apparent at both 240 mg and 360 mg after 2.5 hours and was still present after 6 hours. While this was a small study, it is encouraging that the botanical was effective enough to produce a dose-dependent response.19 Additionally, a study with 262 cognitively intact patients age 60 and older participated in a six-week, randomized, doubleblind, fixed-dose, placebo-controlled, parallel-group, clinical trial with 180 mg per day of Ginkgo biloba. The treatment group showed significantly more improvement on the Selective Reminding Test tasks involving delayed (30 minutes) free recall and recognition of non-contextual, auditory-verbal material, compared with the placebo group. The treatment group also demonstrated significantly greater improvement on the Wechsler Memory Scale-III and Faces II subtest assessing delayed (30 minutes) recognition of visual material (i.e., human faces), compared with the placebo group. In addition, the subjective ratings of overall ability to remember improved significantly in the Ginkgo supplemented group.20
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